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tree.scm
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tree.scm
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;; also git clone https://idiomdrottning.org/tree.scm
;; Copyright 2020 Idiomdrottning, MIT licensed. See LICENSE in the repo.
;; For implementation notes, see README in the repo.
(import (srfi-1) (srfi-8) (srfi-26) (srfi 42) (srfi 69) (srfi 71))
(define (atom? elt) (not (pair? elt)))
(define (tree-walk-preorder proc tree)
(proc tree)
(when (pair? tree)
(for-each
(cut tree-walk-preorder proc <>)
tree)))
(define (tree-walk-postorder proc tree)
(when (pair? tree)
(for-each
(cut tree-walk-postorder proc <>)
tree))
(proc tree))
(define (spair? tree)
(if (pair? tree) tree '()))
(define (tree-walk-breadth-first proc tree)
(proc tree)
(let desc ((tree tree))
(when (pair? tree)
(for-each proc tree)
(desc (append-map spair? tree)))))
(define (tree? tree)
(let ((ht (make-hash-table eq?)))
(call-with-current-continuation
(lambda (break)
(tree-walk-preorder
(lambda (a)
(when (pair? a)
(if (hash-table-exists? ht a)
(break #f)
(hash-table-set! ht a #t))))
tree)
#t))))
(define (tree=? same? tree1 tree2)
(call-with-current-continuation
(lambda (break)
(let desc ((tree1 tree1) (tree2 tree2))
(cond
((and (pair? tree1) (pair? tree2))
(for-each desc tree1 tree2))
((same? tree1 tree2) #t)
(else (break #f))))
#t)))
(define (tree-map proc tree)
(cond
((null? tree) '())
((atom? tree) (proc tree))
(else (map (cut tree-map proc <>) tree))))
(define (tree-copy tree)
(if (atom? tree) tree (map tree-copy tree)))
(define (tree-count pred tree)
(let ((c 0))
(tree-walk-preorder
(lambda (node)
(when (pred node)
(set! c (+ 1 c))))
tree)
c))
(define (tree-size tree)
(tree-count atom? tree))
(define (tree-any? pred tree)
(call-with-current-continuation
(lambda (break)
(tree-walk-preorder
(lambda (node)
(when (pred node)
(break #t)))
tree) #f)))
(define (tree-every? pred tree)
(not (tree-any? (compose not pred) tree)))
(define (tree-find pred tree default)
(call-with-current-continuation
(lambda (break)
(tree-walk-preorder
(lambda (node)
(when (pred node)
(break node)))
tree) default)))
(define (tree-find-equal? tree needle)
(tree-find (cut equal? needle <>) tree #f))
(define (tree-atoms-any? pred tree)
(call-with-current-continuation
(lambda (break)
(tree-walk-preorder
(lambda (node)
(when (and (atom? node) (pred node))
(break #t)))
tree) #f)))
(define (tree-atoms-every? pred tree)
(not (tree-atoms-any? (compose not pred) tree)))
(define (invert-tree tree)
(let ((inversion (make-hash-table eqv?)))
(hash-table-set! inversion tree (list #f 0 #f))
(let desc ((tree tree) (num 1))
(do-ec
(:list subtree (index i) tree)
(if (pair? subtree))
(begin
(hash-table-set! inversion subtree (list tree num i))
(desc subtree (add1 num)))))
inversion))
(define tree-parent (compose first hash-table-ref))
(define tree-depth (compose second hash-table-ref))
(define tree-local-position (compose third hash-table-ref))
(define tree-contains? hash-table-exists?)
(define (tree-c-commands? inversion commanding commanded)
(let ((parent (tree-parent inversion commanding)))
(if (= 1 (count pair? parent))
(tree-c-commands? inversion parent commanded)
(tree-any? (cut eq? commanded <>) parent))))
(define (tree-path inversion subtree)
(if
(tree-contains? inversion subtree)
(cons subtree
(let desc ((parent (tree-parent inversion subtree)))
(if parent
(cons parent (desc (tree-parent inversion parent)))
'())))
#f))
(define (list-replace lis old new)
(if (eq? lis old)
new
(map
(lambda (elt) (if (eq? elt old) new elt))
lis)))
(define (tree-replace-on-path path subtree newnode)
(fold
(lambda (lis old)
(set! newnode (list-replace lis old newnode))
lis)
subtree
(cdr path))
newnode)
(define (tree-replace-on-path-with-values path subtree newnode)
(if (null? path) (values subtree newnode)
(values
(fold
(lambda (lis old)
(set! newnode (list-replace lis old newnode))
lis)
subtree
(cdr path))
newnode)))
(define (tree-replace inversion subtree newnode)
(tree-replace-on-path (tree-path inversion subtree) subtree newnode))
(define (tree-add inversion subtree newnode)
(tree-replace inversion subtree (append subtree (list newnode))))
(define (tree-insert inversion subtree index newnode)
(tree-replace inversion subtree
(receive (before after)
(split-at subtree index)
(append before (list newnode) after))))
(define (tree-prune inversion subtree)
(let ((parent (tree-parent inversion subtree)))
(if parent
(tree-replace inversion parent
(remove (cut eq? subtree <>) parent))
'())))
(define (find-shared-tail lisa lisb)
(let* ((lena (length lisa))
(lenb (length lisb)))
(let desc
((lisa (if (> lena lenb) (take-right lisa lenb) lisa))
(lisb (if (< lena lenb) (take-right lisb lena) lisb)))
(if (eq? (car lisa) (car lisb))
lisa
(desc (cdr lisa) (cdr lisb))))))
(define (tree-move inversion subtree newparent)
(let* ((old-parent (tree-parent inversion subtree))
(full-old-parent-path (tree-path inversion old-parent))
(full-add-path (tree-path inversion newparent))
(shared-tail (find-shared-tail full-old-parent-path full-add-path))
(lenst (length shared-tail))
(old-parent prune-new
(tree-replace-on-path-with-values
(drop-right full-old-parent-path lenst)
old-parent (remove (cut eq? subtree <>) old-parent)))
(newparent parent-with-child
(tree-replace-on-path-with-values
(drop-right full-add-path lenst)
(if (memq newparent full-old-parent-path)
(tree-prune (invert-tree newparent) subtree)
newparent)
(append newparent (list subtree)))))
(tree-replace-on-path
shared-tail
(car shared-tail)
(list-replace
(list-replace
(car shared-tail)
old-parent
prune-new)
newparent parent-with-child))))
(define (composite-tree-move inversion subtree newparent)
(tree-add (invert-tree (tree-prune inversion subtree))
(if (memq newparent (tree-path inversion subtree))
(tree-prune (invert-tree newparent) subtree)
newparent)
subtree))
(define (display2 thing port)
(if (null? port)
(display thing)
(display thing (car port))))
(define (tree-display-atoms tree separator . port)
(define (spacer)
(set! spacer
(lambda () (display2 separator port))))
(tree-walk-breadth-first
(lambda (node)
(when (atom? node)
(spacer)
(display2 node port)))
tree))